There are two related objectives in our study. The first is to describe the relationship between functional magnetic resonance imaging (fMRI) and the underlying neural activity, as measured using electrophysiological recording techniques. We will examine the brains of humans and monkeys using fMRI under similar stimulus conditions, followed by studies of identical stimuli in the same monkeys using electrophysiological recording techniques. Further, the connections of fields active during these experiments will be examined in monkeys using neuroanatomical tracing techniques. The relationship between maps of cortical activity based on fMRI and electrophysiologically defined sensory maps has not been demonstrated for any sensory system in any mammal. Second, we will use this combination of data collection techniques to examine the contribution of the somatosensory system to manual dexterity and bilateral coordination of the hands in humans. The present investigation represents a unique opportunity to securely anchor basic research on sensory neocortex to cognitive science.

In humans, we will use fMRl to locate areas in anterior parietal cortex that are known to respond to simple tactile stimuli and compare these results with fMRI studies in monkeys. Simple stimuli will also be used to determine the number and organization of somatosensory fields in the lateral sulcus and posterior parietal cortex in both humans and monkeys. Then, in humans, areas in the Sylvian fissure and posterior parietal cortex will be studied using complex stimuli such as tactile discrimination, tactile recognition, attention, active touch, and bilateral use of the digits and hands. Briefly, these experiments will consist of brushing the skin of the hand in different directions, tapping one or both hands or digits, or having the subject actively move the digits of one or both hands. In later studies in humans more complex stimuli will be used, such as tasks involving object discrimination or identification of novel versus familiar objects to examine areas of the neocortex involved in tactile recognition and memory. Further, the modulation of activity in cortical fields due to shifting attention will be examined by alternating the attention of the subject between stimulated and non stimulated body parts, and between the stimulated body part and different sensory stimuli (e.g. visual).

In anesthetized macaque monkeys we will use fMRI to examine regions of cortex active during similar simple stimulus paradigms. After monkeys have undergone successful fMRI, their somatosensory cortex will be explored again using electrophysiological recording techniques. In order to accurately relate our electrophysiological findings to fMRI results, plastic, fluid-filled probes will be implanted as landmarks in the neocortex prior to the commencement of fMRI Blood vessels will be imaged using fast multiplanar spoiled gradient recalled echo imaging techniques (FMP SPGR) and photographed prior to electrophysiological recording for comparison. Thus, we can relate fMRI results between monkeys and humans, and more precisely infer how the activity patterns in humans relate to electrophysiological data from monkeys.

Finally, while it is possible to examine the activity patterns of human cortex for a variety of sensory and cognitive tasks, it is not possible to examine the cortical and thalamic interconnections of fields involved in these tasks. However, these patterns can be examined in monkeys. In this series of studies we will describe the patterns of connections of functionally defined fields with other somatosensory fields, motor areas, higher order sensory fields, frontal and prefrontal areas, limbic areas, and temporal lobe areas that project to the amygdala and hippocampus. Thus, we can begin to unravel the circuitry that generates the remarkable sensory and cognitive abilities in humans.